Reproduction and cloning
The genetic information passed from parent to offspring is contained in genes carried by chromosomes in the nucleus. Sexual reproduction produces offspring that resemble their parents, but are not identical to them. Asexual reproduction produces offspring - clones - which are genetically identical to their parents.
Plants can be cloned artificially using cuttings or tissue culture. Animals can be cloned using embryo transplants or fusion cell cloning. Genetic information from one species can be transferred to another species using genetic engineering.
Offspring resemble their parents because they contain genetic information passed on to them by their parents.
A gene is a section of DNA [DNA: The material inside the nucleus of cells, carrying genetic information. DNA stands for Deoxyribonucleic Acid. ] that carries the code for a particular protein. Different genes control the development of different characteristics of an organism. Many genes are needed to carry all the genetic information for a whole organism. Chromosomes, found in the cell nucleus, contain many genes.
The number of genes and chromosomes varies from species to species. For example, cells in human beings have 46 chromosomes that carry about 30,000 genes in each cell; and cells in fruit flies have eight chromosomes that carry about 13,600 genes.